Kbeaner,
I am a taxidermist and I see a lot of weird stuff like that all the time. I believe what you have is a cyst that I have found in many deer. It is not bad if it does not have an odor to it. If it has an odor it is infection from some type of wound or bacteria. The odor from an infected wound is not something that would escape your nose. I would not be afraid of eating your deer, just trim around it and go from there. http://wyomingtaxidermy.blogspot.com/